Field of the Invention
The present invention relates to an abrasive material including manganese dioxide, in particular to an abrasive material including manganese dioxide having a specific particle shape suitable for polishing silicon carbide.
Description of the Related Art
Manganese dioxide is produced, for example, through deposition on an anode by electrolysis, and is used in large amounts as a material for alkali manganese battery. Such particles produced by electrolysis are aggregates of needle crystals (see, Patent Document 1 and Patent Document 2), and there is known a technology to pulverize such aggregates to yield fine needle-like particles.
It has also been known to use as an abrasive material the manganese dioxide needle-like particles produced by such a method (Patent Document 3). Such manganese dioxide needle-like particles obtained by electrolysis are aggregates of approximately 0.1 μm in the long axis, and an abrasive material including such needle-like particles of manganese dioxide is said to be excellent in abrasive performance.
As described above, in the fields of battery materials and abrasive materials, manganese dioxide in the form of needle crystals has been considered to be excellent for the purpose of improving the chemical performances. Abrasive materials including manganese dioxide have higher polishing capability than abrasive materials including silicon oxide or cerium oxide, depending on the objects to be polished. For a to-be-polished object such as an object made of tungsten, difficult to polish, an abrasive material including manganese dioxide has been used (Patent Document 4).
Recently, silicon carbide (SiC) has been attracting attention as a substrate material for power electronics semiconductors and white LEDs; however, silicon carbide has an extremely high hardness and is known as a difficult-to-polish material. For example, an attempt to polish silicon carbide is made with an abrasive material including silicon oxide having an excellent abrasive property; however, the polishing rate is not really high, and the obtained degree of surface precision is also not sufficiently satisfactory. Accordingly, there has been strongly demanded a polishing technology which can rapidly polish a difficult-to-polish material such as silicon carbide and can attain a high degree of surface precision.